Carbon Markets

Carbon markets are trading systems in which greenhouse gas (GHG) emission rights — commonly referred to as carbon credits or allowances — are bought and sold among participants.1 These systems use market-based mechanisms to provide economic incentives for reducing emissions, operating on the principle that limiting pollution will be more efficient if polluters can choose whether to reduce emissions or purchase the right to emit.2

The concept emerged from the Kyoto Protocol (1997), which established the first international framework for carbon trading, and has since evolved into a complex ecosystem comprising both compliance and voluntary markets. As of 2024, the global carbon market encompasses both regulated systems — such as the European Union Emissions Trading System (EU ETS) — and voluntary mechanisms driven by corporate sustainability commitments and the provisions of the Paris Agreement's Article 6.3

History

Origins and Early Development

The theoretical foundations of carbon pricing trace back to the economist Arthur Pigou, who in 1920 introduced the concept of a Pigouvian tax — a levy on activities that generate negative externalities, such as pollution. Pigou argued that by internalizing the external costs of pollution, markets could achieve socially optimal outcomes.4

The practical framework for carbon trading was established by the Kyoto Protocol (adopted in 1997, entered into force in 2005), which created three market-based mechanisms:5

• International Emissions Trading (IET) — Allowed countries with emission reduction targets to trade emission reduction units (ERUs) with one another.
• Clean Development Mechanism (CDM) — Enabled developed countries to invest in emission reduction projects in developing countries and earn certified emission reduction (CER) credits.
• Joint Implementation (JI) — Permitted countries with emission targets to earn emission reduction units (ERUs) by investing in reduction projects in other countries with commitments.

Evolution Through the Compliance Periods

The Kyoto Protocol's first commitment period (2008–2012) saw the EU ETS emerge as the dominant compliance market, covering approximately 11,000 industrial installations across 30 countries. By the second commitment period (2013–2020, known as the Doha Amendment), the architecture had expanded to include additional jurisdictions including New Zealand, Australia (later withdrawn), and South Korea.6

The Paris Agreement (2015) marked a paradigm shift. Unlike Kyoto's top-down approach, Paris established a bottom-up framework of Nationally Determined Contributions (NDCs) and, crucially, Article 6, which provides the framework for international carbon markets under the new regime. Article 6.2 enables internationally transferred mitigation outcomes (ITMOs), while Article 6.4 establishes a new central sustainability mechanism.7

How Carbon Markets Work

Cap-and-Trade Systems

The most common carbon market mechanism is the cap-and-trade system, which operates through four fundamental steps:8

1. Setting the cap: A regulatory authority determines the total allowable level of emissions for a defined set of entities or sectors, typically expressed in tonnes of CO₂ equivalent (CO₂e). The cap usually decreases over time to ensure absolute emission reductions.
2. Distributing allowances: Emission allowances (each typically representing one tonne of CO₂e) are distributed to regulated entities, either through auctioning (sale) or free allocation (grandfathering or benchmarking).
3. Trading: Covered entities trade allowances among themselves. Those who can reduce emissions cheaply sell surplus allowances to those facing higher abatement costs.
4. Compliance: At the end of each compliance period, entities must surrender enough allowances to cover their verified emissions. Shortfalls incur significant penalties.

Baseline and Credit Systems

An alternative mechanism used primarily in voluntary markets is the baseline-and-credit approach. Rather than setting an absolute cap, this system establishes a reference level of emissions (the baseline) that would occur without the project activity. Any emissions reduction achieved below this baseline generates a credit that can be sold.9

Market Structure

Compliance Markets

Compliance carbon markets are established by government regulation and require certain entities — typically large emitters in energy, manufacturing, and transportation sectors — to monitor, report, and limit their greenhouse gas emissions. The major compliance systems as of 2025 include:10

Voluntary Carbon Markets

The voluntary carbon market (VCM) allows corporations, organizations, and individuals to purchase carbon credits to offset their emissions voluntarily, typically as part of corporate ESG (Environmental, Social, and Governance) strategies or net-zero commitments. Unlike compliance markets, there is no regulatory obligation to participate.11

Voluntary carbon credits are generated by projects across several categories:

• Avoidance projects: Preventing emissions that would otherwise occur (e.g., REDD+ — Reducing Emissions from Deforestation and Forest Degradation)
• Removal projects: Actively removing CO₂ from the atmosphere (e.g., direct air capture, enhanced weathering, biochar)
• Renewable energy: Wind, solar, and hydroelectric projects displacing fossil fuel generation
• Community development: Projects providing clean cooking stoves, water purification, or other interventions that reduce emissions

Carbon Pricing

The price of carbon reflects the cost of emitting one additional tonne of CO₂ equivalent. Prices vary dramatically across markets depending on the stringency of the cap, the supply of allowances, and broader economic conditions. Carbon pricing can be achieved through two primary policy instruments:12

Emissions Trading Systems (ETS)

In an ETS, the price of carbon is determined by market supply and demand. The supply side is controlled by the cap, while demand depends on the level of emissions from covered entities. Prices are further influenced by factors including the availability of offset credits, banking and borrowing provisions, and market stabilization mechanisms such as Market Stability Reserves (MSR).13

Carbon Taxes

A carbon tax sets the price directly through legislation, while the resulting level of emission reductions is determined by market responses. As of 2025, over 70 carbon pricing systems have been implemented or announced worldwide, covering approximately 23% of global greenhouse gas emissions.14

Challenges and Criticisms

Credit Quality and Integrity

The voluntary carbon market has faced significant scrutiny over the quality and environmental integrity of many carbon credits. Investigations in 2023–2024 revealed that some offset projects generated credits representing little to no real emission reduction, with estimates suggesting that up to 89% of forestry offsets could be worthless due to flawed methodologies.15

Key integrity concerns include:

• Lack of additionality: Credits issued for projects that would have occurred anyway
• Permanence risks: Carbon removal projects (especially nature-based) face risks of reversal through fires, pestilence, or policy changes
• Double counting: The same emission reduction being claimed by both the project host country and the purchasing entity
• Leakage: Emission reductions in one location leading to increased emissions elsewhere
• Overestimation: Methodologies that overstate the actual emission reductions achieved

Equity and Distributional Concerns

Carbon markets have been criticized for potentially exacerbating global inequities. Developed nations and corporations can purchase offsets in developing countries rather than reducing their own emissions at source, potentially enabling carbon colonialism — the extraction of environmental benefits from the Global South while retaining economic activities that drive emissions in the Global North.16

The European Union's Carbon Border Adjustment Mechanism (CBAM), set to fully implement by 2026, represents a particularly contentious development. By imposing carbon costs on imports from countries without equivalent carbon pricing, the CBAM aims to prevent carbon leakage but has been criticized as a form of green protectionism that could disadvantage developing economies.17

Future Outlook

Article 6 Implementation

The full implementation of Article 6 of the Paris Agreement is expected to be the most significant development in carbon markets in the coming decades. Key provisions include:18

• Article 6.2 (Cooperation approaches): Bilateral or multilateral agreements between countries to transfer emission reductions, governed by corresponding adjustments to prevent double counting.
• Article 6.4 (Sustainable Development Mechanism): A centralized UN-supervised mechanism for generating high-integrity credits, partially replacing the CDM.
• Article 6.8 (Non-market approaches): Recognition that cooperation can also occur through non-market means such as technology transfer and capacity building.

Emerging Trends

Several transformative trends are reshaping the carbon market landscape:

• Tokenization and blockchain: Emerging use of distributed ledger technology to improve transparency, traceability, and liquidity of carbon credits.
• AI and remote sensing: Satellite-based monitoring and machine learning algorithms to verify emission reductions with greater precision and frequency.
• Quality standards: Voluntary adoption of the Integrity Council for the Voluntary Carbon Market (IC-VCM) Core Carbon Principles (CCP) to establish baseline quality standards.
• Corporate procurement: Increasing shift from anonymous spot market purchases to direct project procurement with higher transparency and community benefit.
• Carbon removal demand: Rapidly growing market for permanent CO₂ removal technologies, with prices reaching $300–$600 per tonne for direct air capture.